The following two US patents are aircraft turbofans with valves for the fan output air which select a cruise mode or a high-power mode:
U.S. Pat. No. 3,149,461 has a jet engine which also turns a remote compressor by a driveshaft. The compressed air output of the remote compressor can go to a much larger fan power unit, under control of his valve 15. The compressed air becomes the working fluid for the larger unit. It resembles ours, but some of his air always goes to thrust via his tapping 23.
U.S. Pat. No. 5,275,356 a front fan's outflow travels a fan duct to the exhaust nozzle where it produces thrust for cruise flight. During VTOL flight the nozzle turns down to generate lift; valves divert some fan air to a boost compressor remotely driven by a driveshaft. The boost compressor feeds a combustion chamber whose output powers a lift fan turbine. This is similar to ours, but it takes him two valves to control the front fan output: Valve 102 and fan duct blocking door 122 in his FIG. 2.
Early versions of our main flow control valve:
U.S. Pat. No. 3,016,698 a circumferential ring of hinged, overlapping flaps squeezes down or flares out to send a low pressure compressor output directly to a duct burner or else to a boost compressor in a turbojet.
U.S. Pat. No. 3,280,560 for a preferred shape of the flaps in its FIGS. 5 and 6.
This US patent for a VTOL aircraft powerplant has cycle variability:
U.S. Pat. No. 3,867,813 is a two-spool turbofan whose low-pressure spool turns a large front fan to give extra air mass flow for VTOL operation. Cruising flight is without the extra air. Its FIG. 1 shows mechanical variability of the intake airflow into the core spool, thereby enabling the front fan to supercharge the core engine during VTOL operation. His apparatus is variable-incidence blading in the large front fan. The blading “feathers” to pump no air during cruising flight. We adopt the idea of supercharging but implement it differently.
U.S. Pat. No. 3,472,487 shows a turboshaft engine with a multistage power turbine. The last stages have pivoted doors to bypass working fluid around a stage during certain operating conditions. A bypassed stage also has a freewheel clutch for less churning loss. We use both features.
Lift fan airliner design study, Aviation Week and Space Technology, 7-29-91, page 57: Lift fan placement, second combustion chamber, lift fan turbine, and compressed air duct are in principle the same as ours. However, the compressed air is bleed flow from a bank of gas turbine engines.
The emergency power system when one engine fails during VTOL:
U.S. Pat. No. 3,093,968 Stored monopropellant decomposes to generate substitute working gas for the turbine. Our design goes one step further.